Spin dynamics of a J 1-J 2-K model for the paramagnetic phase of iron pnictides

Rong Yu*, Zhentao Wang, Pallab Goswami, Andriy H. Nevidomskyy, Qimiao Si, Elihu Abrahams

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

We study the finite-temperature spin dynamics of the paramagnetic phase of iron pnictides within an antiferromagnetic J 1-J 2 Heisenberg model on a square lattice with a biquadratic coupling -K (S i S j )2 between the nearest-neighbor spins. Our focus is on the paramagnetic phase in the parameter regime of this J 1-J 2-K model where the ground state is a (π,0) collinear antiferromagnet. We treat the biquadratic interaction via a Hubbard-Stratonovich decomposition and study the resulting effective quadratic-coupling model using both modified spin wave and Schwinger boson mean-field theories; the results for the spin dynamics derived from the two methods are very similar. We show that the spectral weight of dynamical structure factor S(q,ω) is peaked at ellipses in the momentum space at low excitation energies. With increasing energy, the elliptic features expand towards the zone boundary and gradually split into two parts, forming a pattern around (π,π). Finally, the spectral weight is anisotropic, being larger along the major axis of the ellipse than along its minor axis. These characteristics of the dynamical structure factor are consistent with the recent measurements of the inelastic neutron scattering spectra of BaFe 2As 2 and SrFe 2As 2.

Original languageEnglish (US)
Article number085148
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume86
Issue number8
DOIs
StatePublished - Aug 31 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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